Control over the propulsion and maneuver of an airborne vehicle, just like control over land or sea vehicles, requires an ability to selectively generate controllable forces on the vehicle. In the simple case where a hot air balloon is being used as an airborne vehicle, only the lifting force that is necessary to overcome the weight of the balloon can be generated and controlled. Thus, hot air balloons can not be effectively maneuvered. As a practical matter, however, most airborne vehicles need to be maneuverable. To do this, it is necessary to generate forces on the vehicle that will keep it airborne (i.e. lift) and propel it through the air (i.e. thrust). Additionally, it is necessary to generate forces that will establish and maintain a desired altitude for the airborne vehicle in pitch, yaw and roll, as it is being propelled through the air.
For the specific case of a lighter-than-air airship, the lifting force that keeps the airship airborne is a lighter-than-air gas (e.g. helium). In general, the gas that is to provide lift is somehow confined within the fuselage of the airship, much like a hot air balloon. For such a vehicle, however, the maneuver forces that provide control for thrust, pitch, yaw and roll must be provided by other means. Typically, these forces are provided by various combinations of propulsion units (e.g. engine driven propellers), and control surfaces (e.g. rudder, elevator and trim planes). When used in manned airships, where some degree of operational stability is essential for crew effectiveness, typical power plants and control surfaces are quite adequate. On the other hand, if the airship is unmanned, non-traditional power plants may be more effectively employed. This will be particularly so if the airship's fuselage is to be maneuvered and maintained in variously selected orientations for extended periods of time, which might otherwise cause extreme discomfort for an aircrew member.
Examples of applications for an unmanned airship include such uses as advertising and surveillance. For instance, it is apparent that about only one-third of an airship's fuselage surface can be effectively seen by an observer on the ground. On the other hand, an airship that can be maneuvered in roll through 120°, and thereafter selectively held stationary, could effectively present a sequence of three different advertisements to the same viewing audience. In another application, an airship that can be maneuvered to be geo-stationary for a selected period of time, and then conveniently moved to another geo-stationary location, could be useful for a variety of surveillance applications. In these, and all other cases, there are control considerations that need to be addressed. Importantly, in all of these cases, control is provided by the selective application of forces on the airship.
Power plants (i.e. propulsion units) for airborne vehicles are of many types and variations. In all instances, however, they are specifically employed to generate a thrust vector that has both a direction and a magnitude. One particular type of propulsion unit that is of specific interest here, is a so-called cycloidal propulsion unit. Such a unit is disclosed in detail in U.S. application Ser. No. 10/690,284 titled “Cycloidal VTOL UAV,” which is assigned to the same assignee as the present invention and which is incorporated herein, in its entirety. The particularly interesting aspect of such a cycloidal propulsion unit is the fact that it can generate a thrust vector that is located in a definable plane. In particular, a cycloidal propulsion unit can generate a thrust vector of variable magnitude, and establish a direction for the thrust vector that is variable through 360° in the plane. Simply stated, a cycloidal propulsion unit can create a thrust vector that is controllable and variable in both magnitude and direction, in a given plane.
In light of the above, it is an object of the present invention to provide a lighter-than-air airship that incorporates cycloidal propulsion units for producing maneuver and control forces on the airship. Another object of the present invention is to provide an airship with the ability to execute 360° of roll, and maintain a selected orientation in roll for an extended period of time. Yet another object of the present invention is to provide an airship that can selectively move to, and then loiter at, a sequence of geo-stationary locations. Still another object of the present invention is to provide a lighter-than-air airship with cycloidal propulsion units that is relatively easy to manufacture, is simple to operate, and is comparatively cost effective.